A next generation wireless local area network (WLAN) standard 802.11ax is dedicated to further improving WLAN spectral efficiency, an area throughput, actual user experience, and performance in various environments of indoor and outdoor dense network deployment, and requires suppression of interference between devices, so as to meet large-scale and highly-loaded networking requirements.
Specific to an uplink multi-user (UL-MU) sending mode, the industry provides a solution of performing, by using a P-matrix, masking on a high efficiency long training field (HE-LTF), to improve HE-LTF orthogonality. An HE-LTF is a pilot sequence, and a receive end performs channel estimation and frequency offset detection based on a received HE-LTF. The P-matrix includes eight rows of sequences that are corresponding to eight encoded data sequence flows, respectively. A station (STA) performs, by using a corresponding row sequence in the P-matrix and based on a data-flow transport layer allocated by an access point (AP), masking on an HE-LTF that needs to be sent by the STA.
After masking is performed on the HE-LTF by using the P-matrix, a peak-to-average power ratio (PAPR) of the HE-LTF is usually relatively high, and even far greater than a minimum PAPR threshold of a data portion. This affects accuracy of channel estimation and frequency offset detection.